::..Web For U..::: internet

Hyper Text Markup Language (HTML)

HTML was primarily created for displaying textual pages to users. As the growth of WWW HTML is also modified to cop the modern age’s needs.
Still its a presentational language.
To make it dynamic Java Scripts are introduced.

Basic Part of HTML Page:

<html> tag is the root tag of a html page.

<html> tag contains:

<head> tag
<body> tag

Basic Parts of HTML Page <head> tag:

The head element contains meta data information that describes the document itself, or associates it with related resources, such as scripts and style sheets.

<head> Elements:

base
link
meta
script
style
title

Response Header Fields

The first line of the server’s response contains a status code

200 OK   request was processed successfully

301 Moved permanently document has been moved

304 Not modified      if cached version is up-to-date

400 Bad request   syntax error in client’s request

403 Forbidden client is not allowed access (e.g., protected)

404 Not found    file could not be found

500 Internal server error server failed

503 Service unavailable server is overloaded

In addition to the status code, the server’s response may include

Date response time (in GMT)

Server identification info on the server

Last-modified time document was last changed (in GMT)

Content-length size of document, in bytes

Content-type file format (e.g., html, gif, pdf)

Expires prevents browser from caching beyond date

Hyper Text Transfer Protocol (HTTP)

Hypertext Transfer Protocol (HTTP):

application-level protocol for distributed, collaborative, hypermedia information systems
generic, stateless, object-oriented
can be used for many tasks, such as name servers & distributed object management systems
underlying language of the Web

HTTP/1.0 allows only connectionless message passing

each request/response requires a new connection
to download a page with images requires multiple connections

can overload the server, require lots of overhead

HTTP/1.1 provides persistent connection by default

once client & server connect, remains open until told to close it (or timeout)
reduces number of connections, saves overhead
client can send multiple requests without waiting for responses

e.g., can request all images in a page at once

Web is not equal to Internet

Internet : a physical network connecting millions of computers using the same protocols for sharing/transmitting information (TCP/IP)

in reality, the Internet is a network of smaller networks

World Wide Web: a collection of interlinked multimedia documents that are stored on the Internet and accessed using a common protocol (HTTP)

Key distinction: Internet is hardware; Web is software

Many other Internet-based applications exist

e.g., email, telnet, ftp, usenet, some instant messenging services,…

::..Web For U..::

Pages

Friday, October 22, 2010

Hyper Text Markup Language (HTML)

Response Header Fields

Hyper Text Transfer Protocol (HTTP)

Web is not equal to Internet

Popular Posts